A wide variety of disclosures exists in regard to flame retardant additives for polymers, such as polyurethane foams. Two representative examples of disclosures of this type, which relate to blends of two differing flame retardant additives, include the following:
U.S. Pat. No. 4,273,881 to J. G. Otten describes the use of a 50:50 mixture of flame retardant A, sold under the trademark ANTIBLAZE 19, and bis-(2-chloroethyl)-2-chloroethyl-phosphonate (See Col. 9, lines 61-62).
U.S. Pat. No. 3,956,200 to J. Biranowski describes the use of flame retardant blends comprising a polyglycol hydrogen polyphosphonate and an additive, non-reactive flame retardant in a ratio of from about 20:1 to 1:1, preferably from about 5:1 to 1:1.
In addition to the foregoing patent disclosures, certain blends of monomeric and oligomeric flame retardants have also been sold to the polyurethane industry, including compositions carrying the trademarks FYROL 25 and FYROL EFF of Akzo Nobel Chemicals Inc. The product sold under the former mark included an oligomer that contained a blend of both phosphate and phosphonate moieties, whereas the product sold under the latter mark contained a major amount (about 66%) of the oligomeric component and a minor (about 32.5%) of the monomeric flame retardant component.
The flame retardant blends that have been previously described all contain halogen.
In addition to the foregoing, U.S. Pat. No. 5,672,645 to T. Eckel et al. describes a flame retardant blend of a monophosphorus compound, which can either be halogen-containing or non-halogenated, and an oligomeric phosphorus compound. This blend is only described for use in aromatic polycarbonate-containing compositions and not in polyurethane foams.